Gastrointestinal stromal tumors are not exception to this, in that the majority (nearly 85%) of GISTs patients present primary activating mutations in the gene encoding the mast/stem cell growth factor receptor KIT, a type III RTK that plays an essential role in the regulation of cell survival and proliferation, hematopoiesis, stem cell maintenance, gametogenesis, mast cell development, migration and function, and in melanogenesis. This evidence concerns the gene KIT and gastrointestinal stromal tumor.